Catalyzer for the oxidation of ammonia with oxygen or with gases containing oxygen



W; CEDERBERG 1,389,463

CATALYZER FOfi THEOXIDAT ION OF AMMONIA WITH OXYGEN OR ,WITH GASES CONTAINING OXYGEN Filed April 23. 1951 .2 72 2/51: for: i

Z. MCderbe/y Vim/w SGCODC Patented Nov. 29, 1932- IVAB WALFRID OEDERIBERG, OF

DAHLEM,

NEAR BERLIN, GERMANY, ASSIGNOB TO OXYAK KON AKTIENGESELLSCHAFT, OF ZURICH, SWITZERLAND CATALYZTIB FOR THE OXIDATIdN 0E AMMONTA WITH OXYGEN OR WITH GABm GONTAIMNG OXYGEN Application filed April 28 1981, Serial No. 532,392, and in Germany April 30, 1930.

The resent invention relates to a catalyzer made rom platinum or similar metals and...

serving for oxidizing ammonia with oxygenor with ases containing oxy en.

When oxi izing ammonia cata ytically by means of air, the catalyzer usually consists of metal wire nets in the form of gauze. These gauzes are madefrom similar metals or their alloys which usually have a thickness of 0,04 or 0,06 mm. The gauze accordingly has a fineness of 3600 or 1200 meshes per cm At the hitherto used processes of oxidizing ammonia with air the. velocity of the gas current when passing throu h the gauze amounts to 5-20 cm per At such relatively low velocities of flow the mechanicalresistance of nets of the above mentioned kind will be sufficient, provided' that the diameter of the combustion apparatus used is not extraordinarily large. respectively the catalyti- Further, the density cally active surface obtained at such nets will at the said velocities of flow be sufiicient to prevent losses of nitrogen through unburned ammonia. In some modern processes of oxidlzmg ammonia catalytically air has been replacedby pure oxygen or gases rich in oxygen and through this change in oxidizing agent new conditions have been created. Gas mixtures containing ammonia and oxygen are com bustible respectively explosive when the am.- monia content is high and in this case'the gas mixture therefore must flow through the wire gauze at a velocity which is higher than the velocity of combustion of the mixture, in order that back fire or explosions may be safely avoided. The velocities of flow must therefore in this case be much higher than the velocities of the ammonia-air-mixtures hitherto used and usually are up to twenty times as high as the latter or still higher. Further, when oxygen or gases rich in oxygen are used the concentration of the ammonia is up to thrice as high as in the mixtures formerly used and the heat developed during the reaction is therefore much more intense than hitherto. Under these changed conditions of operation'the known wire nets consisting of gauze do not satisfy the rewires of platinum or quirements, because the mechanical resistance force, the capacityof heat and the catalytically active surface of the same are fully insufficient. The employment of such nets will therefore call forth great losses in ammonia and the nets will always be destroyed by burning through. It is of course not pos sible to remove these drawbacks by using wire of greater thickness, because in this case the density of the'nets will be reduced correspondingly, and it is neither possible to increase the strength by arran ing a plurality of nets of extremely fine wire ehind or above each other, because the perviousness to gas through this measure will be reduced so strongly, that the reguiredvvelocity of flow can not be maintaine increased and nets of this kind are therefore extremely well suited for use as contact nets at the catalytical oxidation of ammonia with oxygen or gases rich in oxygen. The weft threads of this fabric may also have a thickness of 0,04 or 0,06 mm, but preferably the weft thread has a thickness of 0,10 or 0,12

mm and the warp thread is 0,020,04 mm' thicker. The capacity of heat of such galloon neetings is 3-15 times as high and the catalytically active surface 23 times as high as at nets of the kind hitherto used. v

For the purpose in question twilled galloon nettings have proven to be especially well suited. Such nets possess a maximal perviousness to gases even at the highest density and these advantageous pro erties are combined with an extraordinari y high mechanical resisting force. Velocities of flow amounting to :more' than 600 cm peri second may be employed without the nets becoming overloaded. When such nets according to the m6 invention are used the combustion apparatus thus has an extremely high capacity, so that the catalytic oxidation of ammonia with oxygen as an oxidation a ent may be executed m a much more e cient manner hitherto.

Two referred forms of catalyzers according to t e invention are shown in the accompanying drawing in which Fig. 1 represents a galloon netting and Fig. 2 represents atwllled alloon netting. In b0 figures, 1 denotes the weft threads I and 2 denotes the warp threads.

I claim:

1. A catalyzer containing metals of th platinum group for the catalytic oxidation of ammonia with oxygen or oxygeneous gases, characterized in this, that it consists of a galloon netting.

2. A catalyzer containing alloys of the platinum group for the catalytic oxidation of ammonia with oxygen or oxygeneous gases, characterized in this, that it consists of a alloon netting.

3. g catalyzer containing platinum for the catalytic oxidation of ammonia with oxy n or oxygeneous gases, characterized in t is, that it consists of a galloon netting.

4. A catalyzer containing metals of the platinum group for the catalytic oxidation of ammonia with oxygen or oxygeneous gases,

characterized in this, that it consists of a twilled galloon netting.

5. A catalyzer containingalloys of the platinum group for the catalytic oxidation of ammonia with oxygen or oxygeneous gases, characterized in this, that it consists of a twilled galloon netting.

6. A catal zer containing platinum for the catalytic oxidation of ammonia with o gen or oxygeneous' gases, characterized in this, that it consists of a twiiled galloon nettin IVAR WALFRID CEDERBERG.

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